1,721,039 research outputs found
Erratum
Get PDFErratum del artículo publicado en Zeitschrift für Naturforschung A 55, 267 (2000). Fil: Errico, Leonardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Fabricius, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Rentería, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin
Electronic, structural, and hyperfine properties of pure and Cd-doped hexagonal La2O3 semiconductor
Get PDFWe present a detailed first-principles study of structural, electronic, and hyperfine properties of pure and Cd-doped lanthanum sesquioxide (La2O3) with the hexagonal structure (A-phase). We calculated the equilibrium structure, the density of states (DOS), the energy band-gap and, finally, the electric-field-gradient (EFG) tensor at the different atomic sites (La, O, and Cd at substitutional La sites) using different approximations for the exchange and correlation potential. In the case of pure A-La2O3 our predictions are compared with available experimental data obtained in X-ray Diffraction experiments and Nuclear Quadrupole Resonance and Nuclear Magnetic Resonance spectroscopies. The excellent agreement between theory and experiments gave us a solid base for the study of Cd-doped A-La2O3. In the case of the doped system, a very good agreement between the predicted and the experimental EFG at the 111Cd sites (obtained in Time-Differential Perturbed γ-γ Angular Correlations experiments) was found. From the comparison of the EFGs obtained at different probe sites we can discuss and elucidate the role played by the electronic structure of the probe atoms, and the structural and electronic modifications induced by the Cd impurity in the La2O3 host, on the origin of the EFG.Fil: Richard, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Errico, Leonardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional del Noroeste de la Provincia de Buenos Aires; ArgentinaFil: Rentería, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin
FP-LAPW calculations of the EFG at Cd Impurities in rutile SnO2
Get PDFWe report an ab initio study of the electric-field gradient (EFG) at Cd impurities located at the cation site in the semiconductor SnO2 (rutile phase). The study was performed with the WIEN97 implementation of the FP-LAPW method. In order to simulate the diluted Cd-impurity in the SnO2 host and to calculate the electronic structure of the system we used a 72-atoms super-cell, studying the relaxation introduced by the impurity in the lattice. The free-relaxation process performed shows that the relaxations of the oxygen nearest-neighbors of the impurity are not isotropic. Our prediction for the EFG tensor are compared with experimental results and point-charge model predictions. Vol: 136/137Fil: Errico, Leonardo Antonio. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Fabricius, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; ArgentinaFil: Rentería, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de Física; Argentin
Atomic surrounding of Co implanted in AlN at high energy
Get PDFAlN bulk ceramic has been implanted with energetic Co ions. In order to accurately characterise the atomic surrounding of the implanted ions, X-ray absorption measurements were carried out at 80 K in the fluorescence mode at the Co K edge in the as-implanted and annealed states. Simulation of the EXAFS oscillations allowed us to identify a first stage where Co is inserted in the AlN matrix followed by a second stage where Co precipitates form.Fil: Traverse, Agnès. Lure, Universidad Paris-sud; FranciaFil: Delobbe, Anne. Lure, Universidad Paris-sud; FranciaFil: Zanghi, Didier. Lure, Universidad Paris-sud; FranciaFil: Rentería, Mario. Lure, Universidad Paris-sud; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Gailhanou, Marc. Lure, Universidad Paris-sud; Franci
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
First-principles study of Cd impurities localized at and near the (001) α-Al2O3 surface
Get PDFAbstract A combination of two first-principles electronic structure calculation methods in the framework of density-functional theory was applied to investigate the (001) α-Al2O3 surface reconstruction and its structural, electronic, magnetic, and hyperfine properties when doped with Cd impurities at different depths from the surface. The SIESTA approach was used to obtain the equilibrium positions of all atoms and the Full-Potential Augmented Plane Wave plus local orbital (FP-APW+lo) method was employed in order to obtain the electronic structure at these equilibrium positions and all the other physical properties. For the most stable (001) α-Al2O3 surface, we have demonstrated that the inclusion of the Cd atom at substitutional Al sites at and near the surface produces a ground state magnetic behavior. The largest principal component V33 of the electric-field-gradient (EFG) tensor at the Cd atom localized just above the α-Al2O3 terrace showed the same [001] orientation and a dominating p-character as Cd does when it is localized at bulk α-Al2O3, but exhibits an anomalous V33 magnitude four times larger than its value in bulk. Just below the surface, the non symmetric structural relaxation around the Cd impurity is responsible for the strong change in the asymmetry, magnitude, and orientation of the EFG tensor. The changes in the hyperfine properties have been correlated with the modifications observed on the electronic charge density at the different Cd sites and on the p-states of the Cd-projected partial density of states. Accordingly, the significant differences on the hyperfine parameters showed for different depths suggest that 111Cd probe-atoms used in Perturbed γ-γ Angular Correlation experiments could be used for evaluating geometrical and electronic distortions, particularly for positions quite close to the reconstructed surface, as well as contributing to studies of growth, adsorption, and diffusion of atoms in oxide surfaces and interfaces.Fil: Darriba, German Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Faccio, Ricardo. Universidad de la República; UruguayFil: Rentería, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Structural, electronic and hyperfine properties on Sm2O3, Eu2O3 and Gd2O3 phases
Get PDFWe present a detailed first-principles study of three rare-earth lanthanide sesquioxides (Ln2O3, Ln = Sm, Eu, and Gd) in the hexagonal A, the monoclinic B, and the cubic C phases. The calculations were performed with the Density Functional Theory (DFT)-based Augmented Plane Wave plus local orbital (APW + lo) method, using the local spin density approximation (LSDA) and the LSDA + U approach to take into account the strongly correlated Ln-4f electrons. We calculated the equilibrium structures and the effect of hydrostatic pressure on them, the density of states (DOS), the energy band-gaps and, finally, the electric-field-gradient (EFG) tensor at the different cationic sites. The obtained predictions reveal that for the three considered Ln2O3 sesquioxides, the C phase is the stable one, with a transition pressure to the A phase of about 1–2 GPa. For each Ln2O3, the predicted properties were compared with those obtained by means of different experimental techniques. We found that the crystal equilibrium volume, bulk modulus and its first pressure derivative obtained with LSDA are in good agreement with previous experimental results. On the other hand, the inclusion of the U term gives a correct description of the insulating ground state of these systems. Concerning the EFG tensor, LSDA and LSDA + U predict similar values for the EFG at each cationic site in all cases. These results are consistent with the hyperfine interactions experiments reported for the B and C phases of Gd2O3. Finally, we analyze the origin of the EFG at Ln sites, by considering the contributions of the different Ln orbitals to it, and its relation with the local structure.Fil: Richard, Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; ArgentinaFil: Errico, Leonardo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires; ArgentinaFil: Rentería, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin
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